We have established a completely operational laboratory in the Lymphokines/Cytokines Section of the LMI. Functional assays for lymphokine activities such as interferon, IL-1, IL-2, IL-3 are operational. We have initiated studies concerning the biological activity of endorphins on human lymphocyte subpopulations. Preliminary data demonstrate that large granular lymphocytes (LGL) as well as T lymphocytes possess a large number of receptors for beta-endorphin. The binding of endorphins to the receptor apparently triggers intracellular events mediated through the metabolism of arachidonic acid. This metabolic pathway also is involved in the cellular response to many other stimulants including IL-2. Conversely, inhibitors of arachidonic acid metabolism change the extracellular levels of cyclic GMP and result in the down-regulation of immunoenhancing lymphokines.